Oxidized low-density lipoproteins impair endothelial function by inhibiting non-genomic action of thyroid hormone-mediated nitric oxide production in human endothelial cells.
Oxidized low-density lipoproteins impair endothelial function by inhibiting non-genomic action of thyroid hormone-mediated nitric oxide production in human endothelial cells.
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DOI：
10.1089/thy.2011.0524
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发表时间：
2013-02
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通讯作者：
R. Vicinanza;G. Coppotelli;C. Malacrino;T. Nardò;B. Buchetti;L. Lenti;F. Celi;S. Scarpa
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作者：
R. Vicinanza;G. Coppotelli;C. Malacrino;T. Nardò;B. Buchetti;L. Lenti;F. Celi;S. Scarpa
背景甲状腺激素（TH）在调节心脏功能（包括收缩性和全身血管阻力（SVR））中起重要作用。3，5，3 '-三碘甲腺原氨酸（T（3））是TH的活性形式，通过PI 3 K/AKT非基因组信号通路诱导内皮型一氧化氮合酶的活化。甲状腺功能减退症与SVR和血清低密度脂蛋白（LDL）水平升高相关，氧化LDL（oxLDL）的蓄积可能损害内皮依赖性血管舒张。本研究的目的是研究天然低密度脂蛋白（nLDL）和氧化低密度脂蛋白（oxLDL）对T（3）介导的AKT磷酸化、一氧化氮（NO）和环磷酸鸟苷（cGMP）生成的影响。方法将人脐静脉内皮细胞暴露于nLDL或oxLDL中3 h，然后用T（3）（10（-7）M）刺激或用维生素E和C的抗氧化剂混合物预处理12 h，再用LDL处理。通过Western印迹分析AKT磷酸化，并通过使用4，5-二氨基荧光素二乙酸酯评价NO产生。用酶免疫法测定细胞内cGMP的产生。用CuSO（4）氧化LDL，用高效液相色谱法测定LDL中α-生育酚的含量。结果：oxLDL损伤T（3）介导的AKT丝氨酸473磷酸化，并显著降低NO（oxLDL+T（3）vs. T（3），9.79±0.5 Au vs. 80.75±2.8 Au，均值±标准差，p<0.0001）和cGMP的产生。此外，用抗氧化剂混合物预处理可消除LDL对T（3）作用的抑制作用。结论：oxLDL可减弱T（3）的非基因组作用，并削弱T（3）对内皮细胞NO和cGMP生成的影响。这些数据表明，oxLDL，除了诱导动脉粥样硬化的过程中，也可能促进外周阻力的T（3）的机制，进一步放大甲状腺功能减退症对内皮功能的影响，通过增加SVR。
BACKGROUND Thyroid hormone (TH) plays an important role in the modulation of cardiac function, including contractility and systemic vascular resistance (SVR). 3,5,3'-triiodothyronine (T(3)), the active form of TH, induces the activation of endothelial nitric oxide synthase via PI3K/AKT non-genomic signaling. Hypothyroidism is associated with an increase in SVR and serum low-density lipoproteins (LDL) levels, and accumulation of oxidized LDL (oxLDL) may impair endothelial-dependent vascular relaxation. The aim of this study was to investigate the effects of both native LDL (nLDL) and oxLDL on T(3)-mediated AKT phosphorylation, nitric oxide (NO), and cyclic guanosine monophosphate (cGMP) production in human endothelial cells. METHODS Human umbilical vein endothelial cells were exposed to either nLDL or oxLDL for 3 hours and then stimulated with T(3) (10(-7) M) or pretreated with an antioxidant mixture of vitamins E and C for 12 hours before treatment with LDL. An analysis of AKT phosphorylation was performed by Western blot, and NO production was evaluated by using 4,5-diaminofluorescein diacetate. Intracellular production of cGMP was measured by enzymatic immunoassay. LDL oxidation was carried out by incubating LDL with CuSO(4), and α-tocopherol content of LDL was evaluated by high-performance liquid chromatography. RESULTS OxLDL impaired T(3)-mediated AKT phosphorylation at serine 473 and significantly decreased the production of both NO (oxLDL+T(3) vs. T(3), 9.79±0.5 AU vs. 80.75±2.8 AU, mean±standard deviation, p<0.0001) and cGMP. Furthermore, pretreatment with the antioxidant mixture obviated the inhibitory effect of LDL on T(3) action. CONCLUSIONS The results of this study demonstrate that oxLDL may contribute to a blunting of the non-genomic action of T(3) and impair the effect of T(3) on NO and cGMP production in endothelial cells. These data suggest that oxLDL, apart from inducing the atherosclerotic process, may also promote a mechanism of peripheral resistance to T(3,) further amplifying the impact of hypothyroidism on endothelial function by increasing SVR.